Pollution Linked to Hospitalizations for Pneumonia in Older Adults

Older adults with long-term exposure
to higher levels of pollution are at higher risk for hospitalization for
pneumonia, according to researchers in Canada.

“Our study found that among older
individuals, long-term exposure to traffic pollution independently increased
their risk of hospitalization for pneumonia,” said principal investigator, Mark
Loeb, M.D., of McMaster University.

The research will be published in
the January 1 issue of the American Thoracic Society’s American Journal of Respiratory and
Critical Care Medicine.

Pneumonia is a leading cause of
sickness and death among older adults, and rates of hospitalizations for
pneumonia among patients 65 and older have been increasing in recent years.

In addition to traffic pollution
associated with roads, Hamilton has a large industrial steel-making complex in
the north end of the city, creating a large exposure zone for residents. The
researchers recruited 365 older adults from Hamilton, Ontario, who had been
hospitalized with radiologically confirmed pneumonia in one of Hamilton’s four
emergency departments between 2003 and 2005. Control subjects from the same
catchment areas as the patients were enrolled contemporaneously, and then
compared their exposures to nitrogen dioxide (NO2), sulfur dioxide
(SO2), and fine particulate matter less that 2.5 μm (PM2.5)
using data from air-quality monitoring stations and land use regression models.

The researchers found that long-term
(more than 12 months) exposures to NO2 and PM2.5 were
each associated with a more than doubled risk of hospitalization from
pneumonia. Individuals with long-term exposure to NO2 had 2.3 times
the risk for hospitalization with pneumonia; for PM2.5, the odds
ratio was 2.26.

“We postulate that long-term
exposure to air pollution may have increased individuals’ susceptibility to
pneumonia by interfering with innate immune defenses designed to protect the
lung from pathogens; this may have included epithelial cell damage, reductions
in bronchial macrophages, or reductions in natural killer cells,” said Dr.
Loeb.

Exposure to SO2 was not
associated with increased risk of hospitalization.

“Given the large population exposure
to ambient air pollution, the results of this study highlight the important
health impact that long-term exposure to ambient air pollution can have on
respiratory infections,” wrote Dr. Loeb. “It also emphasizes the need to
monitor emissions from vehicles, given that ground level NO2 is
derived predominantly from traffic.”

“While we don’t know what is
increasing the rates of pneumonia, we felt that studying air pollution was a
good idea. Assessing if there is a correlation between rising pneumonia rates
and increasing air pollution would be of interest,” said Dr. Loeb.

In future research, Dr. Loeb hopes to examine whether
there is a genetic component to susceptibility to the health effects of
pollution. “Examining genetic variants to see if there is interaction between
genetic basis and air pollution in the causal pathway of pneumonia would be
very interesting,” he said.